(b Montjoie, nr. Aix‐la‐Chapelle, 1777; d Crefeld, 1837).
Ger. silk manufacturer with interest in acoustics. Experimented in measurement of pitch and in 1834 at Stuttgart proposed 440 vibrations for A at 69° F, adopted as ‘Stuttgart pitch’. Invented ‘Aura’, first mouth harmonica, 1816. Writings on subject pubd. 1838.